1. Field of the Invention
The present invention relates to improvement in a semiconductor element such as a semiconductor light-emitting element and improvement in a method for producing the semiconductor element.
2. Description of the Related Art
In a Group III nitride compound semiconductor light-emitting element having an electrically insulating substrate such as a sapphire substrate, two electrodes were formed on the front surface side of the substrate because it was impossible to form any electrode on the rear surface side of the substrate. On this occasion, because of the electrodes, the area for light emission was reduced or it was difficult to obtain any isotropic emission pattern. Hence, the electrodes caused an obstacle to the mode of light emission of the light-emitting element. Moreover, it was necessary to apply wire-bonding to two places so that much labor was required for producing the light-emitting element.
To solve this problem, there has been proposed a semiconductor light-emitting element in which the circumference of an electrically insulating substrate is covered with an electrically conductive material so that electrical conduction is secured between an n electrode and a lead (see Japanese Patent Publication No. Hei. 8-102549 and Japanese Patent Publication No. Hei. No. 6-268258).
In the semiconductor light-emitting element disclosed in Japanese Patent Publication No. Hei. 8-102549, rear and side surfaces of a sapphire substrate and side surfaces of semiconductor layers are covered with an electrically conductive reflecting film. The electrically conductive reflecting film comes into contact with a side surface of an n-type layer. For cutting a wafer into semiconductor light-emitting elements, kerfs are formed in semiconductor layers. The circumferential wall of each kerf serves as side surfaces of semiconductor layers of a corresponding light-emitting element. For this reason, the side surface of the n-type layer is generally rough. Hence, even in the case where an electrically conductive material is laminated on the side surface of the n-type layer, it is difficult to obtain sufficient low-resistance contact between the electrically conductive material and the n-type layer.
On the other hand, the semiconductor light-emitting element disclosed in Japanese Patent Publication No. Hei. 8-268258 is designed, so that an inclined surface is formed around a sapphire substrate, an n electrode is formed on an n-type layer on the inclined surface, and electrically conductive paste used for fixing the light-emitting element to a cup type lead intentionally turns around to the n electrode. It is, however, difficult to grow Group III nitride compound semiconductor layers with good crystallinity on the inclined surface of the sapphire substrate. In the current situation, it is impossible to obtain the light-emitting characteristic required of the light-emitting element.
Further, because the chip scale of the light-emitting element is small, it is difficult to fabricate the light-emitting element under the condition that the electrically conductive paste is not brought into contact to the p-type layer or the p electrode.